Based on the theory of wave propagation and scattering in random medium, the analysis method of the pulse propagating in the plasma medium is presented. Under the condition of strong fluctuations, we have deduced the two-frequency second moment and fourth moment equations, and calculated the two-frequency intensity correlation function and scintillation index in terms of the different electron density spectra. The statistical parameters of the self-correlation function, the correlation bandwidth and time are obtained, in order to provide a basis for studing the characteristic of the pulse propagation in plasma medium.